Mobility management for RRC_INACTIVE user equipment

ABSTRACT

A method for radio access network (RAN) based notification area (RNA) update for a radio resource control (RRC)_INACTIVE user equipment (UE) in an RRC_INACTIVE state is disclosed. The method includes receiving, by the RRC_INACTIVE UE in the RRC_INACTIVE state, a first list of RAN area identities (IDs) from a first cell; receiving, by the RRC_INACTIVE UE in the RRC_INACTIVE state, identification information broadcast by a second cell, the identification information including a RAN area ID of the second cell and a cell ID of the second cell; and transmitting, by the RRC_INACTIVE UE in the RRC_INACTIVE state, at least one of an inactive-radio network temporary identifier (I-RNTI) and a cell ID of the first cell to the second cell, after determining that the RAN area ID of the second cell does not belong to the first list of RAN area IDs.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of U.S. patentapplication Ser. No. 15/894,074 filed on Feb. 12, 2018, which claims thebenefit of and priority to a provisional U.S. Patent Application Ser.No. 62/457,944 filed on Feb. 12, 2017, entitled “MOBILITY MANAGEMENT FORRRC_INACTIVE USER EQUIPMENTS.” The contents of all above-namedapplications are fully incorporated herein by reference for allpurposes.

FIELD

The present disclosure generally relates to wireless communicationmethods, and more particularly, to user equipment initiated radio accessnetwork (RAN) based notification area (RNA) update procedures for thenext generation wireless communication networks.

BACKGROUND

The 3rd Generation Partnership Project (3GPP) has introduced a new radioresource control (RRC) state: RRC_INACTIVE state, for the nextgeneration (e.g., 5th generation (5G)) wireless communication networks.RRC_INACTIVE state aims to achieve power saving with acceptable accesslatency, and is suitable especially for small data transmission such asmachine type communications (MTC) scenarios. When a UE is inRRC_INACTIVE state, the 5G access network (5G-AN) (e.g., including thenext generation radio access network (NG-RAN) and/or non-3GPP accessnetwork connecting to a 5G core network) and the UE store the AccessStratum (AS) context (e.g., UE context) separately. In addition, whenthe UE is in RRC_INACTIVE state, the UE does not have an RRC connectionwith the 5G-AN, although the 5G-AN keeps a connection with the nextgeneration core network (e.g., 5G Core Network (5GC)). Othercharacteristics of RRC_INACTIVE state have been under discussion. Forexample, in RRC_INACTIVE state, the connection between the core networkand the radio access network can be maintained, the radio access networkcan trigger paging of UEs, and no dedicated resources are allocated tothe UEs. As a whole, a UE in RRC_INACTIVE state (e.g., an RRC_INACTIVEUE) may incur minimum signaling, minimum power consumption, and minimumresource costs in the core network (e.g., 5GC) and/or the radio accessnetwork (e.g., 5G-AN).

A RAN-based notification area (RNA) may allow the next generation corenetwork (e.g., 5GC) and the next generation radio access network (e.g.,5G-AN) to know the rough location of an RRC_INACTIVE UE. The RNA mayinclude one or more cells, one or more RAN areas, one or more trackingareas, or any combination thereof. The RNA is UE-specific andconfigurable by the 5G-AN (e.g., by NG-RAN having one or more nextgeneration node Bs (gNBs) and/or one or more next generation evolvednode Bs (ng-eNBs)) using dedicated signaling. It is important for thenext generation radio access network (e.g., 5G RAN, 5G-AN) to be awareof the RRC_INACTIVE UE moving from one RNA to another, and update theRRC_INACTIVE UE's RNA. It should be noted that the RNA update may bedifferent from a core network level location update or a tracking areaupdate, as an RNA is smaller than, equal to, or greater than a trackingarea.

When a UE is in RRC_INACTIVE state, the core network knows the UE'slocation within an RNA and the UE can move within that RNA withoutnotifying the core network. However, without the proper mobilitymanagement, when an RRC_INACTIVE UE is moving out of the coverage of itsanchor gNB, the UE context is not transferred accordingly. Moreover,without the proper mobility management, when the UE moves out of the RNAof its anchor gNB, the anchor gNB cannot find the RRC_INACTIVE UE. As aresult, the RRC_INACTIVE UE cannot quickly reestablish or resume an RRCconnection to a target gNB because the target gNB is out of the RNA ofthe anchor gNB, and does not have the UE context or a connection to theCN. In addition, if the UE moving speed is high or the RNA is small, theUE context transfer and RNA update can become more frequent and causemore overhead. Furthermore, incurring frequent UE context transfer fromone gNB to another in the same RNA, which does not need the UE contextfor DL/UL data transmission, can also cause extra overhead.

Thus, there is a need in the art for UE initiated RNA update proceduresto inform the anchor gNB that the RRC_INACTIVE UE has moved out of itsRNA, to keep the UE context information at least in one gNB of an RNA,and/or to allow the RRC_INACTIVE UE to quickly reestablish or resume anRRC connection with a target gNB for DL/UL transmission, even when thetarget gNB is out of the RNA of the anchor gNB and does not previouslyhave the UE context or a connection to the CN.

SUMMARY

The present disclosure is directed to mobility management forRRC_INACTIVE UEs.

According to an aspect of the present disclosure, a method for RNAupdate for an RRC_INACTIVE UE in an RRC_INACTIVE state is provided. Themethod includes receiving, by the RRC_INACTIVE UE in the RRC_INACTIVEstate, a first list of RAN area identities (IDs) from a first cell;receiving, by the RRC_INACTIVE UE in the RRC_INACTIVE state,identification information broadcast by a second cell, theidentification information including a RAN area ID of the second celland a cell ID of the second cell; and transmitting, by the RRC_INACTIVEUE in the RRC_INACTIVE state, at least one of an inactive-radio networktemporary identifier (I-RNTI) and a cell ID of the first cell to thesecond cell, after determining that the RAN area ID of the second celldoes not belong to the first list of RAN area IDs.

According to an aspect of the present disclosure, a base station for RNAupdate is provided. The base station includes a memory and at least oneprocessor coupled to the memory. The at least one processor isconfigured to transmit identification information of a second cell to anRRC_INACTIVE UE in an RRC_INACTIVE state, the identification including aRAN area ID of the second cell and a cell ID of the second cell; andreceive, from the RRC_INACTIVE UE in the RRC_INACTIVE state, at leastone of a first I-RNTI and a cell ID of a first cell during an RNA updateprocedure with the RRC_INACTIVE UE in the RRC_INACTIVE state.

According to an aspect of the present disclosure, a UE in anRRC_INACTIVE state for RNA update is provided. The UE includes a memoryand at least one processor coupled to the memory. The at least oneprocessor is configured to receive a first list of RAN area IDs from afirst cell; receive identification information broadcast by a secondcell, the identification information including a RAN area ID of thesecond cell and a cell ID of the second cell; and transmit at least oneof an I-RNTI and a cell ID of the first cell to the second cell, afterdetermining that the RAN area ID of the second cell does not belong tothe first list of RAN area IDs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the exemplary disclosure are best understood from thefollowing detailed description when read with the accompanying figures.Various features are not drawn to scale, dimensions of various featuresmay be arbitrarily increased or reduced for clarity of discussion.

FIG. 1A shows a schematic diagram of an RRC_INACTIVE UE moving from ananchor gNB in a first RNA toward a target gNB in a second RNA through asingle assistant gNB in the second RNA, according to an exemplaryimplementation of the present application.

FIG. 1B shows a schematic diagram of an RRC_INACTIVE UE moving from ananchor gNB in a first RNA toward a target gNB in a second RNA throughmultiple RAN-based notification areas, according to an exemplaryimplementation of the present application.

FIG. 2 is an RRC state transition diagram illustrating various RRC statetransition procedures that a UE may undergo within a next generationradio access network, according to an exemplary implementation of thepresent application.

FIG. 3A is a diagram illustrating an RRC Resume procedure achieved by a2-step radio access procedure, according to an exemplary implementationof the present application.

FIG. 3B is a diagram illustrating an RRC Resume procedure achieved by a4-step radio access procedure, according to an exemplary implementationof the present application.

FIG. 4 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, according to an exemplary implementation of the presentapplication.

FIG. 5 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, according to an exemplary implementation of the presentapplication.

FIG. 6 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, where the RAN notification list is determined by theanchor gNB and/or the assistant gNB, according to an exemplaryimplementation of the present application.

FIG. 7 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, where the RAN notification list is determined by ahybrid of the CN and the assistant gNB with key mapping between the CNand the assistant gNB, according to an exemplary implementation of thepresent application.

FIG. 8 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, where the RAN notification list is determined by the CNand the anchor gNB and/or the assistant gNB, with the anchor gNBforwarding the RAN notification list to the assistant gNB, according toan exemplary implementation of the present application.

FIG. 9 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of an RNA in which the anchorgNB is not situated, according to an exemplary implementation of thepresent application.

FIG. 10 is a diagram illustrating a UE initiated RNA update procedurefor an RRC_INACTIVE UE moving within or out of the RNA in which theanchor gNB is not situated, according to another exemplaryimplementation of the present application.

FIG. 11 is a diagram illustrating a UE initiated RNA update procedurefor an RRC_INACTIVE UE moving within or out of the RNA in which theanchor gNB is situated, where the assistant gNB cannot find and/orconnect to the anchor gNB directly, according to an exemplaryimplementation of the present application.

FIG. 12 is a diagram illustrating DL data notification via the anchorgNB, according to an exemplary implementation of the presentapplication.

FIG. 13 is a diagram illustrating DL data notification directly to theassistant gNB, according to an exemplary implementation of the presentapplication.

FIG. 14 is a diagram illustrating UL data from the RRC_INACTIVE UE tothe target gNB, which includes assistant gNB update and UE contexttransfer, according to an exemplary implementation of the presentapplication.

FIG. 15 illustrates a block diagram of a node for wirelesscommunication, in accordance with various aspects of the presentapplication.

DETAILED DESCRIPTION

The following description contains specific information pertaining toexemplary embodiments in the present disclosure. The drawings in thepresent disclosure and their accompanying detailed description aredirected to merely exemplary embodiments. However, the presentdisclosure is not limited to merely these exemplary embodiments. Othervariations and embodiments of the present disclosure will occur to thoseskilled in the art. Unless noted otherwise, like or correspondingelements among the figures may be indicated by like or correspondingreference numerals. Moreover, the drawings and illustrations in thepresent disclosure are generally not to scale, and are not intended tocorrespond to actual relative dimensions.

The following description contains specific information pertaining toexemplary implementations in the present disclosure. The drawings in thepresent disclosure and their accompanying detailed description aredirected to merely exemplary implementations. However, the presentdisclosure is not limited to merely these exemplary implementations.Other variations and implementations of the present disclosure willoccur to those skilled in the art. Unless noted otherwise, like orcorresponding elements among the figures may be indicated by like orcorresponding reference numerals. Moreover, the drawings andillustrations in the present disclosure are generally not to scale, andare not intended to correspond to actual relative dimensions.

For the purpose of consistency and ease of understanding, like featuresare identified (although, in some examples, not shown) by numerals inthe exemplary figures. However, the features in differentimplementations may be differed in other respects, and thus shall not benarrowly confined to what is shown in the figures.

The description uses the phrases “in one implementation,” or “in someimplementations,” which may each refer to one or more of the same ordifferent implementations. The term “coupled” is defined as connected,whether directly or indirectly through intervening components, and isnot necessarily limited to physical connections. The term “comprising,”when utilized, means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in theso-described combination, group, series and the equivalent.

Additionally, for the purposes of explanation and non-limitation,specific details, such as functional entities, techniques, protocols,standard, and the like are set forth for providing an understanding ofthe described technology. In other examples, detailed description ofwell-known methods, technologies, system, architectures, and the likeare omitted so as not to obscure the description with unnecessarydetails.

Persons skilled in the art will immediately recognize that any networkfunction(s) or algorithm(s) described in the present disclosure may beimplemented by hardware, software or a combination of software andhardware. Described functions may correspond to modules which may besoftware, hardware, firmware, or any combination thereof. The softwareimplementation may comprise computer executable instructions stored oncomputer readable medium such as memory or other type of storagedevices. For example, one or more microprocessors or general-purposecomputers with communication processing capability may be programmedwith corresponding executable instructions and carry out the describednetwork function(s) or algorithm(s). The microprocessors orgeneral-purpose computers may be formed of applications specificintegrated circuitry (ASIC), programmable logic arrays, and/or using oneor more digital signal processor (DSPs). Although some of the exemplaryimplementations described in this specification are oriented to softwareinstalled and executing on computer hardware, nevertheless, alternativeexemplary implementations implemented as firmware or as hardware orcombination of hardware and software are well within the scope of thepresent disclosure.

The computer readable medium includes but is not limited to randomaccess memory (RAM), read only memory (ROM), erasable programmableread-only memory (EPROM), electrically erasable programmable read-onlymemory (EEPROM), flash memory, compact disc read-only memory (CD ROM),magnetic cassettes, magnetic tape, magnetic disk storage, or any otherequivalent medium capable of storing computer-readable instructions.

A radio communication network architecture (e.g., a long term evolution(LTE) system, a LTE-Advanced (LTE-A) system, or a LTE-Advanced Prosystem) typically includes at least one base station, at least one userequipment (UE), and one or more optional network elements that provideconnection towards a network. The UE communicates with the network(e.g., a core network (CN), an evolved packet core (EPC) network, anEvolved Universal Terrestrial Radio Access network (E-UTRAN), aNext-Generation Core (NGC), or an internet), through a radio accessnetwork (RAN) established by the base station.

It should be noted that, in the present application, a UE may include,but is not limited to, a mobile station, a mobile terminal or device, auser communication radio terminal. For example, a UE may be a portableradio equipment, which includes, but is not limited to, a mobile phone,a tablet, a wearable device, a sensor, or a personal digital assistant(PDA) with wireless communication capability. The UE is configured toreceive and transmit signals over an air interface to one or more cellsin a radio access network.

A base station may include, but is not limited to, a node B (NB) as inthe UMTS, an evolved node B (eNB) as in the LTE-A, a radio networkcontroller (RNC) as in the UMTS, a base station controller (BSC) as inthe GSM/GSM Enhanced Data rates for GSM Evolution (EDGE) radio accessNetwork (GERAN), a ng-eNB as in an E-UTRAN base station in connectionwith the 5GC, a next generation node B (gNB) as in the 5G-AN, and anyother apparatus capable of controlling radio communication and managingradio resources within a cell. The base station may connect to serve theone or more UEs through a radio interface to the network.

A base station may be configured to provide communication servicesaccording to at least one of the following radio access technologies(RATs): Worldwide Interoperability for Microwave Access (WiMAX), GlobalSystem for Mobile communications (GSM, often referred to as 2G), GSMEDGE radio access Network (GERAN), General Packet Radio Service (GPRS),Universal Mobile Telecommunication System (UMTS, often referred to as3G) based on basic wideband-code division multiple access (W-CDMA),high-speed packet access (HSPA), LTE, LTE-A, eLTE (evolved LTE), NewRadio (NR, often referred to as 5G), and/or LTE-A Pro. However, thescope of the present application should not be limited to theabove-mentioned protocols.

The base station is operable to provide radio coverage to a specificgeographical area using a plurality of cells forming the radio accessnetwork. The base station supports the operations of the cells. Eachcell is operable to provide services to at least one UE within its radiocoverage. More specifically, each cell (often referred to as a servingcell) provides services to serve one or more UEs within its radiocoverage, (e.g., each cell schedules the downlink and optionally uplinkresources to at least one UE within its radio coverage for downlink andoptionally uplink packet transmissions). The base station cancommunicate with one or more UEs in the radio communication systemthrough the plurality of cells. A cell may allocate sidelink (SL)resources for supporting proximity service (ProSe). Each cell may haveoverlapped coverage areas with other cells.

As discussed above, the frame structure for NR is to support flexibleconfigurations for accommodating various next generation (e.g., 5G)communication requirements, such as enhanced mobile broadband (eMBB),massive machine type communication (mMTC), ultra reliable communicationand low latency communication (URLLC), while fulfilling highreliability, high data rate and low latency requirements. The orthogonalfrequency-division multiplexing (OFDM) technology as agreed in 3GPP mayserve as a baseline for NR waveform. The scalable OFDM numerology, suchas the adaptive sub-carrier spacing, the channel bandwidth, and theCyclic Prefix (CP) may be also used for NR. Additionally, two codingschemes are considered for NR: (1) low-density parity-check (LDPC) codeand (2) Polar Code. The coding scheme adaption may be configured basedon the channel conditions and/or the service applications.

Moreover, it is also considered that in a transmission time interval TXof a single NR frame, a downlink (DL) transmission data, a guard period,and an uplink (UL) transmission data should at least be included, wherethe respective portions of the DL transmission data, the guard period,the UL transmission data should also be configurable, for example, basedon the network dynamics of NR. In addition, sidelink resource may alsobe provided in a NR frame to support ProSe services.

In various implementations of the present application, UE context withina serving gNB contains information regarding roaming and accessrestrictions which were provided either at connection establishment orat the last tracking area update. The UE context may include, but is notlimited to, UE Aggregate Maximum Bit Rate, the received HandoverRestriction List, the received UE Security Capabilities, the receivedSecurity Key, etc. In addition, I-RNTI (inactive-radio network temporaryidentifier) is a unique identification used to identify the UE contextfor RRC_INACTIVE UE. In various implementations of the presentapplication, the I-RNTI may be included in an RRC resume ID. In variousimplementation of the present application, the I-RNTI may include therequired information to identify the UE context for RRC_INACTIVE UE. Therequired information may also be included in the RRC resume ID.

In various implementations of the present application, an anchor gNB maybe the last serving gNB of a UE, before the UE transitioned toRRC_INACTIVE state. The anchor gNB may keep the UE context and theUE-associated connection with the core network (e.g., serving AMF(Access & Mobility management Function) and/or UPF (User PlaneFunction)). The UE in RRC_INACTIVE state may remain in ConnectionManagement (CM)-CONNECTED, and may move within an RNA without notifyingthe RAN (e.g., NG-RAN). However, when the RRC_INACTIVE UE moves out ofthe RNA in which the anchor gNB is situated, the RRC_INACTIVE UE mayinitiate an RNA update, among other things, to notify the anchor gNB. Insome other embodiments, when the RRC_INACTIVE UE moves within the RNAwhere the anchor gNB is situated, in some situations (e.g., a timerexpires), the RRC_INACTIVE UE may initiate an RNA update, among otherthings, to notify the anchor gNB or another gNB within the RNA on whichthe RRC_INACTIVE UE now camps.

In various implementations of the present application, an assistant gNBmay be a gNB other than the anchor gNB. The RRC_INACTIVE UE may camp onthe assistant gNB. The assistant gNB may be in the same RNA or in adifferent RNA than the RNA in which the anchor gNB is situated. Theassistant gNB may notify the anchor gNB of the UE's presence in its RNA.The assistant gNB may have the UE's RAN area ID, RNA ID, or the UE's RANnotification list, which includes a list of cell IDs, a list of cells, alist of RAN area IDs, a list of RAN areas, a list of tracking area IDs,or any combination thereof. The assistant gNB may also update the RNA tothe UE. In some embodiments, the RAN area ID may include at least one ofthe tracking area identity and RAN area code (RANAC).

A target gNB may be a gNB other than the anchor gNB. The RRC_INACTIVE UEmay camp on the target gNB. The target gNB may be in the same RNA or ina different RNA than the RNA in which the anchor gNB is situated. TheRRC_INACTIVE UE may attempt to access the target gNB. Upon successfullyretrieving the UE Context of the RRC_INACTIVE UE from the anchor gNB(e.g., through one or more assistant gNB), the target gNB may become theserving gNB for downlink (DL) and/or uplink (UL) transmission. It shouldbe noted that, in various implementations of the present application,either the anchor gNB or the target gNB can also be the assistant gNB.

As described in various implementations of the present application, a UEmay receive cell IDs broadcast by an assistant gNB or a target gNB.However, it should be understood that cell ID is just an example of whata RAN notification list may include. As described herein, a RANnotification list may also include RAN area IDs, tracking area IDs, etc.In some embodiments, the RAN notification list includes the RAN areaIDs, thus, the gNBs may broadcast their RAN area IDs. In someembodiments, the RAN notification list includes the tracking area IDs,thus, the gNBs may broadcast their tracking area IDs.

FIG. 1A shows a schematic diagram of an RRC_INACTIVE UE moving from ananchor gNB in a first RNA toward a target gNB in a second RNA through asingle assistant gNB in the second RNA, according to an exemplaryimplementation of the present application. As shown in FIG. 1A, awireless communication system 100A includes a user equipment (UE) 102,an anchor gNB 104 having a gNB coverage area 112, an assistant gNB 106having a gNB coverage area 114, and a target gNB 110 of the UE 102having a gNB coverage area 118, where the anchor gNB 104, assistant gNB106, and target gNB 110 can access a core network (CN) 130, such as anext generation core network (e.g., 5GC). It is noted that the anchorgNB 104 is within a first RAN-based notification area, RNA1, while theassistant gNB 106 and target gNB 110 are within a second RAN-basednotification area, RNA2, that is different from RNA1. In the presentexemplary implementation, RNA1 and RNA2 are neighboring RAN-basednotification areas. In other exemplary implementations, RNA1 and RNA2may not be immediately adjacent neighboring RAN-based notificationareas.

When the UE 102 is in RRC_INACTIVE state, it does not have an RRCconnection with the anchor gNB 104. The UE 102 may remain in connectionmanagement (CM) connected (e.g., CM-CONNECTED), and move within an areaconfigured by the NG-RAN, such as an RNA, without a need to notify theNG-RAN. The anchor gNB 104, as the last serving gNB, stores the UEcontext of the UE 102, and has a connection (e.g., S1-MME in 4G wirelessnetwork, UE-associated next generation (NG) connection in a 5G wirelessnetwork, such as N2 to AMF and N3 to UPF, etc.) to the CN 130 (e.g.,serving AMF and/or UPF). Both the RRC_INACTIVE UE 102 and the anchor gNB104 keep the UE context, but without an RRC connection between them. Inaddition, when the UE 102 is in RRC_INACTIVE state, as the RRC_INACTIVEUE 102 is moving away from the gNB coverage area 112 of the anchor gNB104 under RNA1 to the gNB coverage area 114 of the assistant gNB 106under RNA2, the anchor gNB 104 may not have knowledge that the UE 102 isleaving or has left its gNB coverage area 112. As such, if withoutproper cross-RNA (inter-RNA) mobility management, the UE context may notbe transferred from the anchor gNB 104 under RNA1 to the assistant gNB106 and/or the target gNB 110 under RNA2. In addition, if without propercross-RNA mobility management, when the RRC_INACTIVE UE 102 moves out ofRNA1, the anchor gNB 104 may not be able to find the RRC_INACTIVE UE102.

FIG. 1B shows a schematic diagram of an RRC_INACTIVE UE 102 moving froman anchor gNB 104 in a first RNA (RNA 1) toward a target gNB 110 in afourth RNA, (RNA 4) through multiple RAN-based notification areas,according to an exemplary implementation of the present application. Asshown in FIG. 1B, a wireless communication system 100B includes a userequipment (UE) 102, an anchor gNB 104 having a gNB coverage area 112, afirst assistant gNB₁ 106 having a gNB coverage area 114, a secondassistant gNB₂ 108 having a gNB coverage area 116, and a target gNB 110having a gNB coverage area 118, where the anchor gNB 104, firstassistant gNB₁ 106, second assistant gNB₂ 108, and target gNB 110 canaccess a CN 130, such as a next generation core network (e.g., 5GC). Itis noted that the anchor gNB 104, first assistant gNB₁ 106, secondassistant gNB₂ 108, and target gNB 110, are within RNA1, RNA2, RNA3, andRNA4, respectively. That is, the RRC_INACTIVE UE 102 moves from the gNBcoverage area 112 of the anchor gNB 104 within RNA1 across multipleassistant gNB coverage areas (e.g., the assistant gNB coverage areas 114and 116) and/or multiple RNAs (e.g., RNA2 and RNA3) before it needs thetarget gNB 110 for UL and DL transmission. In particular, as shown inFIG. 1B, the UE 102 is moving from the gNB coverage area 114 of theassistant gNB₁ 106 toward the gNB coverage area 116 of the assistantgNB₂ 108.

Similar to FIG. 1A, when the UE 102 is in RRC_INACTIVE state, it doesnot have an RRC connection with the anchor gNB 104. The UE 102 mayremain in connection management (CM) connected (e.g., CM-CONNECTED), andmove within an area configured by the NG-RAN, such as an RNA, without aneed to notify the NG-RAN. The anchor gNB 104, as the last serving gNB,stores the UE context of the UE 102, and has a connection (e.g., S1-MMEin a 4G wireless network, UE-associated next generation (NG) connectionin a 5G wireless network, such as N2 to AMF and N3 to UPF, etc.) to theCN 130 (e.g., AMF and/or UPF). Both the RRC_INACTIVE UE 102 and theanchor gNB 104 keep the UE context, but without an RRC connectionbetween them. In addition, when the UE 102 is in RRC_INACTIVE state, asthe RRC_INACTIVE UE 102 is moving from the gNB coverage area 114 of thefirst assistant gNB₁ 106 under RNA2 to the gNB coverage area 116 of theassistant gNB₂ 108 under RNA3, the anchor gNB 104 and the assistant gNB₁106 may not have the knowledge that the UE 102 is leaving or has leftthe gNB coverage area 114.

As such, without proper cross-RNA mobility management, the UE contextmay not be transferred from the first assistant gNB₁ 106 under RNA2 tothe second assistant gNB₂ 108 under RNA3 and/or the target gNB 110 underRNA4. In addition, without proper cross-RNA mobility management, whenthe RRC_INACTIVE UE 102 moves out of RNA2, neither the anchor gNB 104nor the first assistant gNB₁ 106 may be able to find the RRC_INACTIVE UE102.

Thus, for both the diagram 100A in FIG. 1A and the diagram 100B in FIG.1B, it is desirable to have one or more UE initiated procedures totransfer the UE context and update the RNA when the RRC_INACTIVE UE 102moves out of the current RNA, so that the RRC_INACTIVE UE 102 canquickly reestablish or resume an RRC connection with a target gNB 110,even though the target gNB 110 is out of the RNA of the anchor gNB 104and does not previously have the UE context and/or a connection to theCN 130.

In both FIGS. 1A and 1B, the anchor gNB 104 is a gNB, to which all thedata for the RRC_INACTIVE UE 102 routes, because the anchor gNB 104 hasa UE-associated connection with the core network 130 (e.g., a S1-MMEconnection in a 4G network, or a UE-associated next generation (NG)connection in a 5G wireless network, such as N2 to AMF and N3 to UPF).For implementations of the present application, it is assumed thatRRC_INACTIVE state comes after RRC_CONNECTED state, as shown in FIG. 2 .The anchor gNB 104 stores the UE context and maintains a connection(e.g., S1-MME in a 4G wireless network, UE-associated next generation(NG) connection in a 5G wireless network, such as N2 to AMF and N3 toUPF, etc.) to the CN 130 (e.g., AMF and/or UPF). The assistant gNB 106is the first gNB, on which the RRC_INACTIVE UE 102 camps, in the same ora new RAN based notification area. The assistant gNB 106 may notify theanchor gNB 104 of the UE's 102 presence in its coverage area. Theassistant gNB 106 may have the UE's 102 RAN area ID, RNA ID, or the UE's102 RAN notification list, which includes a list of cell IDs, a list ofcells, a list of RAN area IDs, a list of RAN areas, a list of trackingarea IDs, or any combination thereof. The assistant gNB 106 may alsoupdate the RNA to the UE 102. The target gNB 110 is a gNB, on which theRRC_INACTIVE UE 102 camps, when DL/UL transmission is to happen. Itshould be noted that the anchor gNB 104 or the target gNB 110 may alsobe the assistant gNB 106. Moreover, from the UE's 102 perspective, insome embodiments, there is only one anchor gNB 104, which may keep theUE context, a connection to the core network, the UE's 102 assistant gNB106 cell ID and/or the UE's 102 RAN area ID, RNA ID, or the UE's 102 RANnotification list, which includes a list of cell IDs, a list of cells, alist of RAN area IDs, a list of RAN areas, a list of tracking area IDs,or any combination thereof.

In both FIGS. 1A and 1B, the target gNB 110 and the anchor gNB 104 arenot in the same RNA. It should be noted that, from the UE's 102perspective, in some embodiments, there is only one assistant gNB 106existent at any given time in one RAN based notification area in bothcases depicted in FIGS. 1A and 1B.

Among other differences, FIG. 1A shows a single assistant gNB 106between the anchor gNB 104 and the target gNB 110, while FIG. 1B showsmultiple assistant gNBs (106, 108) and multiple RNAs (RNA 1, RNA 2, RNA3, RNA 4) between the anchor gNB 104 and the target gNB 110. In FIG. 1A,the RRC_INACTIVE UE 102 is moving out of RNA1 in which the anchor gNB104 is situated. In FIG. 1B, the RRC_INACTIVE UE 102 is moving out ofRNA 2 in which the assistant gNB₁ 106 is situated, instead of RNA 1 inwhich the anchor gNB 104 is situated as shown in FIG. 1A.

It should be noted that although FIGS. 1A and 1B illustrate embodimentswhere the anchor gNB 104 is in a different RNA than the assistant gNBs(106, 108) and/or target gNB 110, it should be understood that thepresent application is not limited to the illustrated scenarios. Thatis, the RNA update procedures described in the present application maybe also applicable when the assistant gNBs (106, 108) and the target gNB110 are in the same RNA as the anchor gNB 104.

FIG. 2 is an RRC state transition diagram illustrating various RRC statetransition procedures that a UE may undergo within a next generationradio access network, according to an exemplary implementation of thepresent application. The RRC state transition diagram 200 includesRRC_CONNECTED state 262, RRC_INACTIVE state 264, and RRC_IDLE state 266.As shown in FIG. 2 , a UE may transition among RRC_CONNECTED state 262,RRC_INACTIVE state 264, and RRC_IDLE state 266 through variousprocedures (e.g., procedures a, b, c, d, and e). It should be noted thatin the RRC state transition diagram 200, a UE may not transitiondirectly from RRC_IDLE state 266 to RRC_INACTIVE state 264. That is,RRC_INACTIVE state 264 always comes after RRC_CONNECTED state 262. Forexample, the UE may transition from RRC_CONNECTED state 262 toRRC_INACTIVE state 264 through an RRC Suspend procedure (e.g., procedurec). Conversely, the UE may transition from RRC_INACTIVE state 264 toRRC_CONNECTED state 262 through an RRC Resume procedure (e.g., procedured).

In the present application, a next generation radio access network(e.g., 5G-RAN) may configure a UE to send an RRC Resume Request during a2-step random access channel (RACH) procedure as described withreference to FIG. 3A, or a 4-step RACH procedure as described withreference to FIG. 3B. It is noted that the term “RACH procedure(s)” andthe term “RA procedure(s)” may be interchangeably utilized in thepresent disclosure.

FIG. 3A is a diagram illustrating an RRC Resume procedure 300A achievedby a 2-step radio access procedure, according to an exemplaryimplementation of the present application. Diagram 300A includes a UE302 and a target gNB 310. In some implementations, the target gNB 310may be substantially similar to any of the assistant gNB/gNB₁ 106,assistant gNB₂ 108, and target gNB 110 shown in FIGS. 1A and 1B. Inaction 340, the UE 302 may multiplex a preamble sequence in MSG 1 withan RRC Resume Request in MSG 1 (e.g., RRC Connection Resume Request kindof message, RRC Connection Resume Request message, RRC Resume Requestmessage). The target gNB 310 may receive the RRC Resume Request in theMSG1 of random access (RA) procedure. In some implementations, for smallpacket transmission, the UE 302 may indicate that “the cause of RRCResume Request=UL small packet transmission,” and the small data may bemultiplexed with the preamble and the RRC Resume Request message in theMSG1. In action 342, the target gNB 310 may deliver an RRC ResumeResponse to the UE 302 in the MSG2 (e.g., RRC Resume message, RRCConnection Resume message) of RA procedure. For UL small packettransmission, the target gNB 310 may provide an acknowledge(ACK)/non-acknowledgement (NACK) message in the MSG2 to indicate whetherthe target gNB 310 has received the small packet in MSG1 successfully.If the UE 302 successfully completes the RRC resume procedure, the UE302 may further send MSG3 (e.g., RRC Resume Complete message, RRCConnection Resume Complete message) to the target gNB 310. Although themessages in a 2-step radio access procedure are identified as “MSG1” and“MSG2” in FIG. 3A, in the present disclosure, the “MSG1” and “MSG2” in a2-step radio access procedure may also refer to “Message A (MSGA)” and“Message B (MSGB),” respectively.

FIG. 3B is a diagram illustrating an RRC Resume procedure 300B achievedby a 4-step radio access procedure, according to an exemplaryimplementation of the present application. Diagram 300B includes a UE302 and a target gNB 310. In action 350, the UE 302 may send a Preamble(e.g., a random access preamble) to the target gNB 310 through MSG1. Inaction 352, the target gNB 310 may send a Random Access Response inMSG2, if the target gNB 310 decodes MSG1 successfully. In MSG2, thetarget gNB 310 may send configured radio resource information for the UE302 to deliver MSG3 (e.g., RRC Connection Resume Request kind ofmessage, RRC Connection Resume Request message, RRC Resume Requestmessage). In action 354, the UE 302 may deliver an RRC Resume Request inMSG3 to the target gNB 310. In some implementations, for small packettransmission, the UE 302 may indicate that “the cause of RRC ResumeRequest=UL small packet transmission,” and the small data may bemultiplexed with the RRC Resume Request message in MSG 3. In someembodiments, the UE 302 may indicate that the “the cause of RRC ResumeRequest=RNA update”. In action 356, the target gNB 310 may deliver anRRC Resume Response through MSG4 (e.g., RRC Resume message, RRCConnection Resume message) to the UE 302. For UL small packettransmission, the target gNB 310 may provide an ACK/NACK message in theMSG4 to indicate whether the target gNB 310 has received the smallpacket in MSG3 successfully. If the UE 302 successfully completes theRRC resume procedure, the UE 302 may further send MSG5 (not explicitlyshown) (e.g., RRC Resume Complete message, RRC Connection ResumeComplete message) to the target gNB 310. It should be noted that each ofthe 2-step and 4-step RA procedures can be applied to the RNA updateprocedures, for example, in both cases depicted in FIGS. 1A and 1B.

Case 1 UE Initiated RAN-Based Notification Area Update

A UE initiated RAN-based notification area (RNA) update enables anRRC_INACTIVE UE 302 to quickly reestablish or resume an RRC connectionwith a target gNB 310 when needed (e.g., inter-RNA update, intra-RNAupdate, periodic RNA update, etc.). In one implementation, anRRC_INACTIVE UE 302 may initiate an RNA update (e.g., an inter-RNAupdate), as the RRC_INACTIVE UE 302 moves out of an anchor gNB and/or anassistant gNB (FIGS. 1A and 1B), even when the target gNB 310 is out ofthe RNA in which the anchor gNB or the assistant gNB is situated anddoes not previously have the UE context or a connection to a corenetwork. In another implementation, the RRC_INACTIVE UE 302 may initiatean RNA update (e.g., an intra-RNA update), as the RRC_INACTIVE UE 302moves from an anchor gNB to a target gNB 310 within the same RNA. Inanother implementation, an RRC_INACTIVE UE 302 may initiate RNA updateperiodically. For example, the UE 302 initiates an RNA update procedure,when a timer expires.

Case 1-A: RRC_INACTIVE UE Moving within or Out of RNA in which AnchorgNB is Situated

FIG. 4 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, according to an exemplary implementation of the presentapplication. Diagram 400 includes a UE 402, an anchor gNB 404, anassistant gNB 406, and a CN 430 (e.g., a 5GC). In the presentimplementation, the UE 402, anchor gNB 404, assistant gNB 406, and CN430 in FIG. 4 may substantially correspond to the UE 102, anchor gNB104, assistant gNB 106, and CN 130, respectively, in FIG. 1A. In anotherimplementation, the UE 402 may move from the anchor gNB 404 to theassistant gNB 406, where the anchor gNB 404 and the assistant gNB 406are in the same RNA. In such case, the UE 402 may initiate an RNA updateprocedure periodically, for example, when a timer expires.

Diagram 400 also shows actions 460, 462, 464, 466, 468, 470, and 472,for a UE initiated RNA update procedure as the RRC_INACTIVE UE 402 ismoving within or out of the RNA in which the anchor gNB 404 is situated.In action 460, the RRC_INACTIVE UE 402 receives the assistant gNB 406'scell ID (the assistant gNB 406's RAN area ID or the assistant gNB 406'stracking area ID) broadcast from the assistant gNB 406. When theRRC_INACTIVE UE 402 compares the assistant gNB 406's cell ID (theassistant gNB 406's RAN area ID or the assistant gNB 406's tracking areaID) with the cell IDs (RAN area IDs or tracking area IDs) stored in itsRAN notification list, the RRC_INACTIVE UE 402 may determine that it ismoving or has moved out of the original RNA in which the anchor gNB 404is situated. As a result, the RRC_INACTIVE UE 402 initiates an RNAupdate, to inform the anchor gNB 404 about the exit of the RRC_INACTIVEUE 402 and to update the RAN notification list.

In action 462, after determining that the received broadcast cell ID(RAN area ID or tracking area ID) from the assistant gNB 406 is not onits RAN notification list, the RRC_INACTIVE UE 402 initiates a randomaccess channel (RACH) procedure with the assistant gNB 406. The RACHprocedure may be either the 2-step RACH procedure or the 4-step RACHprocedure as described with reference to FIGS. 3A and 3B, respectively.The RRC_INACTIVE UE 402 may send its RRC resume ID and/or I-RNTI and theanchor gNB 404's cell ID (RAN area ID or tracking area ID) either inMSG1 of the 2-step RACH procedure shown in FIG. 3A, or in MSG1/MSG 3 ofthe 4-step RACH procedure shown in FIG. 3B. The assistant gNB 406 maykeep a table including a list of RRC resume IDs and/or I-RNTIs andanchor gNB cell IDs (RAN area IDs or tracking area IDs) in matchingpairs, as the assistant gNB 406 may be an assistant gNB for multipleRRC_INACTIVE UEs.

In action 464, upon receiving the RRC resume ID and/or I-RNTI from theRRC_INACTIVE UE 402, which is new to the assistant gNB 406, theassistant gNB 406 sends an RNA Update message to the anchor gNB 404,where the RNA Update message includes the RRC resume ID and/or I-RNTIfrom the UE 402. The anchor gNB 404 receives the RNA Update message fromthe assistant gNB 406 and keeps a table of UE ID and assistant gNB 406'scell ID (RAN area ID or tracking area ID), so that the anchor gNB 404knows where the RRC_INACTIVE UE 402 is located. The anchor gNB 404 alsokeeps the stored UE context.

In action 466, the anchor gNB 404 sends a UE-specific RNA Request to theCN 430 (e.g., 5G-CN, 5GC or NG-CN), where the UE-specific RNA Requestincludes the RRC_INACTIVE UE 402's UE ID and the assistant gNB 406'scell ID (RAN area ID or tracking area ID), and a key. In oneimplementation, the key can be the security key in the UE context. Inanother implementation, the key can be in other formats, such asUE-specific IDs that the anchor gNB 404 creates and delivers to both theCN 430 via a UE-specific RNA Request and the assistant gNB 406 using anRNA Response. The key is subsequently used by the assistant gNB 406 toensure the integrity of the CN 430, and to confirm that a receivedUE-specific RNA Response from the CN 430 and a received RNA Responsefrom the anchor gNB 404 correspond to the UE 402.

In action 468, the anchor gNB 404 sends an RNA Response including thekey to the assistant gNB 406. In action 470, the CN 430 sends aUE-specific RNA Response including the key and a new RNA having a listof gNB cell IDs (a list of gNB RAN area IDs or a list of gNB trackingarea IDs) to the assistant gNB 406. For example, based on the receivedUE ID, the CN 430 checks the UE context and determines the new RNA forthe RRC_INACTIVE UE 402. When the key in the received RNA Response fromthe anchor gNB 404 matches the key in the received UE-specific RNAResponse from the CN 430, the assistant gNB 406 performs the remainingactions of the RACH procedure. In action 472, the assistant gNB 406transmits the new RNA having the list of gNB cell IDs (e.g., with theassistant gNB 406's cell ID) (the list of gNB RAN area IDs (e.g., withthe assistant gNB 406's RAN area ID), or the list of gNB tracking areaIDs (e.g., with the assistant gNB 406's tracking area ID)), to theRRC_INACTIVE UE 402, using either MSG2 of the 2-step RACH procedureshown in FIG. 3A, or MSG2/MSG4 of the 4-step RACH procedure shown inFIG. 3B.

It is noted that, in the present implementation, the RAN notificationlist is determined by the CN 430. The present implementation alsoutilizes key mapping between the assistant gNB 406 and the CN 430 toensure the integrity of the CN 430, and to confirm that the receivedUE-specific RNA Response from the CN 430 and the RNA Response from theanchor gNB 404 correspond to the UE 402.

FIG. 5 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, according to an exemplary implementation of the presentapplication. Diagram 500 includes a UE 502, an anchor gNB 504, anassistant gNB 506, and a CN 530. In the present implementation, the UE502, anchor gNB 504, assistant gNB 506, and CN 530 in FIG. 5 maysubstantially correspond to the UE 102, anchor gNB 104, assistant gNB106, and core network (CN) 130 in FIG. 1A, respectively. In anotherimplementation, the UE 502 may move from the anchor gNB 504 to theassistant gNB 506, where the anchor gNB 504 and the assistant gNB 506are in the same RNA. In such case, the UE 502 may initiate an RNA updateprocedure periodically, for example, when a timer expires.

Diagram 500 also shows actions 560, 562, 564, 566, 568, 570, and 572 fora UE initiated RNA update procedure as the RRC_INACTIVE UE 502 is movingwithin or out of the RNA in which the anchor gNB 504 is situated. In thepresent implementation, the actions 560, 562, 564, and 572 may besubstantially similar to the actions 460, 462, 464, and 472,respectively, as shown in FIG. 4 . Different from FIG. 4 , in action566, the anchor gNB 504 sends a UE-specific RNA Request to the CN 530(e.g., 5GC, 5G CN), where the UE-specific RNA Request includes theRRC_INACTIVE UE 502's UE ID (without the assistant gNB 506's cell ID(RAN area ID or tracking area ID) or a key). In action 568, the CN 530sends a UE-specific RNA Response including a new RNA having a list ofgNB cell IDs (a list of gNB RAN area IDs or a list of gNB tracking areaIDs) to the anchor gNB 504. For example, based on the received UE ID,the CN 530 checks the UE context and determines the new RNA for theRRC_INACTIVE UE 502. In action 570, the anchor gNB 504 sends an RNAResponse including the new RNA having the list of gNB cell IDs (e.g.,with the assistant gNB 506's cell ID) (the list of gNB RAN area IDs(e.g., with the assistant gNB 506's RAN area ID), or the list of gNBtracking area IDs (e.g., with the assistant gNB 506's tracking areaID)), to the assistant gNB 506. Thus, in the UE initiated RNA updateprocedure illustrated in FIG. 5 , the anchor gNB 504 forwards ortransfers the UE's RAN notification list from the CN 530 to theassistant gNB 506. There is no key mapping between the CN 530 and theassistant gNB 506.

It should be noted that, for implementations of the present application,an RRC_INACTIVE UE's RAN notification list may be determined (1) by aCN, (2) by one or more gNBs, or (3) by a combination of a CN and one ormore gNBs. In one implementation, a CN determines the RRC_INACTIVE UE'sRAN notification list based on the UE context and/ortracking/registration area configured for the UE. For example, thetracking/registration area may be provided by the CN through AMF toNG-RAN (e.g., gNB). The gNB may take into account the UEtracking/registration area when configuring the RNA. As described abovewith reference to FIGS. 4 and 5 , the RRC_INACTIVE UE 402 and 502's RANnotification lists are determined by the core networks 430 and 530,respectively. In the second approach, one or more gNBs, such as anassistant gNB and/or an anchor gNB, can determine the RRC_INACTIVE UE'sRAN notification list based on the UE context and the gNB's connectioncapability to other gNBs. For example, some gNBs may belong to ablacklist of the assistant/anchor gNB, which means that theassistant/anchor gNB cannot communicate with gNBs on its blacklist.Thus, certain cell IDs (RAN area IDs or tracking area ID) on theblacklist may not be included or be removed from the RRC_INACTIVE UE'sRAN notification list.

FIG. 6 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, where the RAN notification list is determined by theanchor gNB and/or the assistant gNB, according to an exemplaryimplementation of the present application. Diagram 600 includes a UE602, an anchor gNB 604, an assistant gNB 606, and a CN 630. In thepresent implementation, the UE 602, anchor gNB 604, assistant gNB 606,and CN 630 in FIG. 6 may substantially correspond to the UE 102, anchorgNB 104, assistant gNB 106, and CN 130, respectively, in FIG. 1A. Inanother implementation, the UE 602 may move from the anchor gNB 604 tothe assistant gNB 606, where the anchor gNB 604 and the assistant gNB606 are in the same RNA. In such case, the UE 602 may initiate an RNAupdate procedure periodically, for example, when a timer expires.

Diagram 600 also shows actions 660, 662, 664, 666, 668, and 670 for a UEinitiated RNA update procedure as the RRC_INACTIVE UE 602 is movingwithin or out of the RNA in which the anchor gNB 604 is situated. In thepresent implementation, the actions 660, 662, and 664 may besubstantially similar to the actions 560, 562, and 564, respectively, asshown in FIG. 5 . Different from FIG. 5 , in action 666, the anchor gNB604 determines the UE 602's new RAN notification list based on the UEcontext, and sends the new RAN notification list to the assistant gNB606. The assistant gNB 606 may filter and/or revise the new RANnotification list based on its connection to other gNBs. For example,the assistant gNB 606 may filter and/or remove the gNB cell IDs (RANarea IDs or tracking area IDs) on the new RAN notification list that ison its blacklist, as indicated in action 668. In action 670, theassistant gNB 606 sends the RAN notification list with the filteredand/or revised gNB cell IDs (RAN area IDs or tracking area IDs) to theUE 602.

In the third approach, a CN and one or more gNBs may determine theRRC_INACTIVE UE's RAN notification list. For example, the CN determinesthe RRC_INACTIVE UE's RAN notification list based on the UE contextand/or tracking area. Then, the one or more gNBs, such as an assistantgNB and/or an anchor gNB, can modify the RRC_INACTIVE UE's RANnotification list determined by the CN based on the UE context and theassistant gNB and/or anchor gNB's connection capability to other gNBs.For example, some gNBs may belong to a blacklist of the assistant/anchorgNB, which means that the assistant/anchor gNB cannot communicate withgNBs on its blacklist. Thus, certain cell IDs (RAN area IDs or trackingarea IDs) on the blacklist may not be included or be removed from theRRC_INACTIVE UE's RAN notification list.

FIG. 7 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of the RNA in which the anchorgNB is situated, where the RAN notification list is determined by ahybrid of the CN and the assistant gNB with key mapping between the CNand the assistant gNB, according to an exemplary implementation of thepresent application. Diagram 700 includes a UE 702, an anchor gNB 704,an assistant gNB 706, and a CN 730. In the present implementation, theUE 702, anchor gNB 704, assistant gNB 706, and CN 730 in FIG. 7 maysubstantially correspond to the UE 102, anchor gNB 104, assistant gNB106, and core network (CN) 130, respectively, in FIG. 1A. In anotherimplementation, the UE 702 may move from the anchor gNB 704 to theassistant gNB 706, where the anchor gNB 704 and the assistant gNB 706are in the same RNA. In such case, the UE 702 may initiate an RNA updateprocedure periodically, for example, when a timer expires.

Diagram 700 shows actions 760, 762, 764, 766, 768, 770, 772, and 774 fora UE initiated RNA update procedure as the RRC_INACTIVE UE 702 is movingwithin or out of the RNA in which the anchor gNB 704 is situated. In thepresent implementation, the actions 760, 762, 764, 766, 768, and 770 maybe substantially similar to the actions 460, 462, 464, 466, 468, and470, respectively, as shown in FIG. 4 . Different from FIG. 4 , inaction 772, after the CN 730 determines the UE 702's new RANnotification list and sends the new RAN notification list to theassistant gNB 706, the assistant gNB 706 may filter and/or revise thenew RAN notification list based on its connection capability to othergNBs. For example, the assistant gNB 706 may filter and/or remove thegNB cell IDs (RAN area IDs or tracking area IDs) on the new RANnotification list that is on its blacklist, as indicated in action 772.In action 774, the assistant gNB 706 sends the RAN notification listwith the filtered and/or revised gNB cell IDs (RAN area IDs or trackingarea IDs) to the UE 702.

In another implementation, the CN determines the UE's new RANnotification list and delivers it to the anchor gNB, the anchor gNB andthe assistant gNB can filter and/or revise the UE's RAN notificationlist, as illustrated in FIG. 8 . FIG. 8 is a diagram illustrating a UEinitiated RNA update procedure for an RRC_INACTIVE UE moving within orout of the RNA in which the anchor gNB is situated, where the RANnotification list is determined by the CN and the anchor gNB and/or theassistant gNB, with the anchor gNB forwarding the RAN notification listto the assistant gNB, according to an exemplary implementation of thepresent application. Diagram 800 includes a UE 802, an anchor gNB 804,an assistant gNB 806, and a CN 830. In the present implementation, theUE 802, anchor gNB 804, assistant gNB 806, and CN 830 in FIG. 8 maysubstantially correspond to the UE 102, anchor gNB 104, assistant gNB106, and CN 130, respectively, in FIG. 1A. In another implementation,the UE 802 may move from the anchor gNB 804 to the assistant gNB 806,where the anchor gNB 804 and the assistant gNB 806 are in the same RNA.In such case, the UE 802 may initiate an RNA update procedureperiodically, for example, when a timer expires.

Diagram 800 shows actions 860, 862, 864, 866, 868, 870, 872, 874 and 876for a UE initiated RNA update procedure as the RRC_INACTIVE UE 802 ismoving within or out of the RNA in which the anchor gNB 804 is situated.In the present implementation, the actions 860, 862, 864, 866, and 868may be substantially similar to the actions 560, 562, 564, 566, and 568,respectively, as shown in FIG. 5 . Different from FIG. 5 , in action870, after the CN 830 determines the UE 802's new RAN notification listand sends the new RAN notification list to the anchor gNB 804, theanchor gNB 804 filters and/or revises the new RAN notification listbased on its connection capability to other gNBs. For example, theanchor gNB 804 filters and/or removes the gNBs on the new RANnotification list that is on its blacklist, as indicated in action 870.In action 872, the anchor gNB 804 sends the RAN notification list withthe filtered and/or revised gNB cell IDs (RAN area IDs or tracking areaIDs) to the assistant gNB 806. In action 874, the assistant gNB 806further filters and/or revises the already filtered/revised RANnotification list from the anchor gNB 804 based on the assistant gNB806's connection capability to other gNBs. For example, in action 874,the assistant gNB 806 may filter and/or remove the gNB cell IDs (RANarea IDs or tracking area IDs) on the already filtered/revised RANnotification list that is on its blacklist. In action 876, the assistantgNB 806 sends the RAN notification list with the further filtered and/orrevised gNB cell IDs (RAN area IDs or tracking area IDs) to the UE 802.

In one implementation, the size of RAN notification list implies the RANnotification area coverage. In one implementation, that RAN notificationlist may also comprise numerous beams, which have the cell IDs in theRAN notification list. As such, any beam in the RAN notification listmay serve as an anchor gNB/assistant gNB/target gNB. In oneimplementation, the RAN notification list implies the RAN area IDs,which form the UE's RAN notification area coverage. In oneimplementation, each RAN area ID may be a cell ID, a list of cell IDs,or any form of RAN-based ID (e.g., a RAN area ID, a list of RAN areaIDs, a tracking/notification area ID, or a list of tracking/notificationarea IDs). For example, a RAN area ID may represent a RAN area, whichmay be a subset of a CN tracking/notification area.

Case 1-B: RRC_INACTIVE UE Moving within or Out of an RNA in which AnchorgNB is not Situated

FIG. 9 is a diagram illustrating a UE initiated RNA update procedure foran RRC_INACTIVE UE moving within or out of an RNA in which the anchorgNB is not situated, according to an exemplary implementation of thepresent application. Diagram 900 includes a UE 902, an anchor gNB 904,an assistant gNB₁ 906, an assistant gNB₂ 908, and a CN 930. In thepresent implementation, the UE 902, anchor gNB 904, assistant gNB₁ 906,assistant gNB₂ 908, and CN 930 in FIG. 9 may substantially correspond tothe UE 102, anchor gNB 104, assistant gNB₁ 106, assistant gNB₂ 108 andCN 130, respectively, in FIG. 1B. In another implementation, the UE 902may move from the assistant gNB₁ 906 to the assistant gNB₂ 908, wherethe assistant gNB₁ 906 to the assistant gNB₂ 908 are in the same RNA. Insuch case, the UE 902 may initiate an RNA update procedure periodically,for example, when a timer expires.

Diagram 900 also shows actions 960, 962, 964, 966, 968, 970, 972, 974and 976 for a UE initiated RNA update procedure as the RRC_INACTIVE UE902 moves within or out of the RNA in which the assistant gNB₁ 906 issituated. Initially, the RRC_INACTIVE UE 902 may keep receiving thebroadcast cell IDs (RAN area IDs or tracking area IDs) and may camp onany gNB with the received broadcast cell IDs (RAN area IDs or trackingarea IDs). For example, in action 960, the RRC_INACTIVE UE 902 receivesthe cell ID (RAN area ID or tracking area ID) of the assistant gNB₂ 908broadcast from the assistant gNB₂ 908. When the RRC_INACTIVE UE 902compares the cell ID (RAN area ID or tracking area ID) of the assistantgNB₂ 908 with the cell IDs (RAN area IDs or tracking area IDs) stored inits RAN notification list, the RRC_INACTIVE UE 902 determines that it ismoving or has moved out of the RNA in which the assistant gNB₁ 906 issituated. As a result, the RRC_INACTIVE UE 902 initiates an RNA update,to remove the information of the RRC_INACTIVE UE 902 stored on the firstassistant gNB (e.g., the assistant gNB₁ 906) by using a UE AssistanceDelete message from the anchor gNB, (e.g., the anchor gNB 904), and toupdate the RAN notification list. In action 962, after determining thatthe received broadcast cell ID (RAN area ID or tracking area ID) fromthe assistant gNB₂ 908 is not in its RAN notification list, theRRC_INACTIVE UE 902 initiates a RACH procedure with the assistant gNB₂908. The RACH procedure can be the 2-step RACH or the 4-step RACHdescribed with reference to FIGS. 3A and 3B, respectively. TheRRC_INACTIVE UE 902 may send its RRC resume ID and/or I-RNTI and theanchor gNB cell ID (RAN area ID or tracking area ID) in either MSG 1 inFIG. 3A or MSG 3 in FIG. 3B. The assistant gNB₂ 908 may keep a tableincluding a list of RRC resume IDs and/or I-RNTIs and anchor gNB cellIDs (RAN area IDs or tracking area IDs) in matching pairs, as theassistant gNB₂ 908 may be an assistant gNB for multiple RRC_INACTIVEUEs. In action 964, upon receiving the RRC resume ID and/or I-RNTI fromthe RRC_INACTIVE UE 902, which is new to the assistant gNB₂ 908, theassistant gNB₂ 908 sends an RNA Update message to the anchor gNB 904,where the RNA Update message includes the received RRC resume ID and/orI-RNTI from the UE 902. The anchor gNB 904 receives the RNA Updatemessage from the assistant gNB₂ 908 and updates the table of UE ID andthe assistant gNB₂ 908's cell ID (RAN area ID or tracking area ID), sothat the anchor gNB 904 knows where the RRC_INACTIVE UE 902 is located.The anchor gNB 904 still keeps the stored UE context.

In action 966, the anchor gNB 904 sends a UE-specific RNA Request to theCN 930 (e.g., 5GC), where the UE-specific RNA Request includes theRRC_INACTIVE UE 902's UE ID, the assistant gNB₂ 908's cell ID (RAN areaID or tracking area ID), and a key. The format and functionality of thekey may be substantially similar to the key described with reference toFIG. 4 . In action 968, the anchor gNB 904 sends a UE Assistance Deletemessage having the RRC resume ID and/or I-RNTI to the assistant gNB₁906. As a result, the assistant gNB₁ 906 deletes the information of theRRC_INACTIVE UE 902. That is, the RRC_INACTIVE UE 902 is to have onlyone assistant gNB at a time. In action 970, after deleting theinformation of the RRC_INACTIVE UE 902, the assistant gNB₁ 906 replies aUE Assistance Delete Confirm message to the anchor gNB 904. As such, theinformation of the RRC_INACTIVE UE 902 stored on the assistant gNB₁ 906is removed by using the UE Assistance Delete message from the anchor gNB904.

In action 972, the anchor gNB 904 sends an RNA Response including thekey to the assistant gNB₂ 908. Based on the received UE ID from action966, the CN 930 checks the UE context and determines a new RNA for theRRC_INACTIVE UE 902. In action 974, the CN 930 sends a UE-specific RNAResponse, including the key and the new RNA having a list of gNB cellIDs (a list of gNB RAN area IDs or a list of gNB tracking area IDs), tothe assistant gNB₂ 908. The present implementation also utilizes keymapping between the assistant gNB₂ 908 and the CN 930 to ensure theintegrity of the CN 930, and to confirm that the received UE-specificRNA Response from the CN 930 and the RNA Response from the anchor gNB904 correspond to the UE 902. In action 976, the assistant gNB₂ 908 thentransmits the new RNA, which include the list of gNB cell IDs (e.g.,with the assistant gNB₂'s cell ID) (the list of gNB RAN area IDs (e.g.,with the assistant gNB₂ 908's RAN area ID), or the list of gNB trackingarea IDs (e.g., with the assistant gNB₂ 908's tracking area ID)), to theRRC_INACTIVE UE 902, using MSG 2 in FIG. 3A or MSG 4 in FIG. 3B. Assuch, the RAN notification list is updated.

FIG. 10 is a diagram illustrating a UE initiated RNA update procedurefor an RRC_INACTIVE UE moving within or out of the RNA in which theanchor gNB is not situated, according to another exemplaryimplementation of the present application. Diagram 1000 includes a UE1002, an anchor gNB 1004, an assistant gNB₁ 1006, an assistant gNB₂1008, and a CN 1030. In the present implementation, the UE 1002, anchorgNB 1004, assistant gNB₁ 1006, assistant gNB₂ 1008, and CN 1030 in FIG.10 may substantially correspond to the UE 102, anchor gNB 104, assistantgNB₁ 106, assistant gNB₂ 108 and CN 130, respectively, in FIG. 1B. Inanother implementation, the UE 1002 may move from the assistant gNB₁1006 to the assistant gNB₂ 1008, where the assistant gNB₁ 1006 to theassistant gNB₂ 1008 are in the same RNA. In such case, the UE 1002 mayinitiate an RNA update procedure periodically, for example, when a timerexpires.

Diagram 1000 also shows actions 1060, 1062, 1064, 1066, 1068, 1070,1072, 1074, and 1076 for a UE initiated RNA update procedure as theRRC_INACTIVE UE 1002 moves within or out of the RNA in which theassistant gNB₁ 1006 is situated. In contrast to FIG. 9 , the informationof the RRC_INACTIVE UE 1002 stored on the first assistant gNB (e.g., theassistant gNB₁ 1006) is removed by using a UE Assistance Delete messagefrom the second assistant gNB (e.g., the assistant gNB₂ 1008). In action1062, the UE 1002 sends RRC resume ID and/or I-RNTI, anchor gNB 1004'scell ID (RAN area ID or tracking area ID) and the assistant gNB₁ 1006'scell ID (RAN area ID or tracking area ID) to the assistant gNB₂ 1008,for example, in either MSG 1 in FIG. 3A or MSG 3 in FIG. 3B. As aresult, in action 1072, the assistant gNB₂ 1008 can send a UE AssistanceDelete message to the assistant gNB₁ 1006 directly. That is, theRRC_INACTIVE UE 1002 is to have only one assistant gNB at a time. Inaction 1074, after deleting the information of the RRC_INACTIVE UE 1002,the assistant gNB₁ 1006 replies a UE Assistance Delete Confirm messageto the assistant gNB₂ 1008. As such, the information of the RRC_INACTIVEUE 1002 stored on the assistant gNB₁ 1006 is removed by using the UEAssistance Delete message from the assistant gNB₂ 1008.

Similar to FIG. 9 , the RRC_INACTIVE UE initiated RNA update procedurealso updates the RAN notification list. As shown in FIG. 10 , thepresent implementation also utilizes key mapping between the assistantgNB₂ 1008 and the CN 1030 to ensure the integrity of the CN 1030, and toconfirm that the received UE-specific RNA Response from the CN 1030 andthe RNA Response from the anchor gNB 1004 correspond to the UE 1002.

As discussed above, the implementations of the present application underCase 1-A have three approaches for RAN notification list determination,namely, by a CN, by one or more gNBs, and by a CN and one or more gNBs;and two approaches for RAN notification list delivery, namely, the CNdelivering to the assistant gNB through key mapping, and the anchor gNBforwarding the RAN notification list. It should be understood that theabovementioned approaches for RAN notification list determination andfor RAN notification list delivery may also be applied for Case 1-B.

FIG. 11 is a diagram illustrating a UE initiated RNA update procedurefor an RRC_INACTIVE UE moving within or out of the RNA in which theanchor gNB is situated, where the assistant gNB cannot find and/orconnect to the anchor gNB directly, according to an exemplaryimplementation of the present application. Diagram 1100 includes a UE1102, an anchor gNB 1104, an assistant gNB 1106, and a CN 1130. In thepresent implementation, the UE 1102, anchor gNB 1104, assistant gNB1106, and CN 1130 in FIG. 11 may substantially correspond to the UE 102,anchor gNB 104, assistant gNB 106, and CN 130 in FIG. 1A, respectively.In another implementation, the UE 1102 may move from the anchor gNB 1104to the assistant gNB 1106, where the anchor gNB 1104 and the assistantgNB 1106 are in the same RNA. In such case, the UE 1102 may initiate anRNA update procedure periodically, for example, when a timer expires.

Diagram 1100 also shows actions 1160, 1162, 1164, 1166, 1168, 1170,1172, 1174, and 1176 for a UE initiated RNA update procedure as theRRC_INACTIVE UE 1102 moves within or out of the RNA in which the anchorgNB 1104 is situated. As shown in FIG. 11 , in action 1164, theassistant gNB 1106 cannot find and/or connect to the anchor gNB 1104directly. For example, the assistant gNB 1106 has no direct connectionto the anchor gNB 1104. Or, the assistant gNB 1106 is on the blacklistof the anchor gNB 1104. In such circumstances, the assistant gNB 1106may find and connect to the anchor gNB 1104 through the CN 1130.

As shown in FIG. 11 , in action 1166, the assistant gNB 1106 sends aUE-specific RNA Request to the CN 1130 (e.g., 5G CN), where theUE-specific RNA Request includes the RRC_INACTIVE UE 1102's UE ID andthe anchor gNB 1104's cell ID (RAN area ID or tracking area ID). Afterthe CN 1130 finds the anchor gNB 1104 through the anchor gNB 1104's cellID (RAN area ID or tracking area ID) in the UE-specific RNA Request, theCN 1130 notifies the anchor gNB 1104 by sending an RNA Update message tothe anchor gNB 1104 in action 1168. Thereafter, in action 1170, an XnSetup may be performed between the assistant gNB 1106 and anchor gNB1104. The Xn Setup may include the interaction between the assistant gNB1106 and the anchor gNB 1104, for example, to establish an Xn interface.For example, the Xn Setup may include XN SETUP REQEUST message, XN SETUPRESPONSE message and/or XN SETUP FAILURE message.

In the present implementation, the CN determines the RAN notificationlist. It should be noted that the three approaches for RAN notificationlist determination and two approaches for RAN notification list deliverycan also be applied, when the assistant gNB cannot find or connected tothe anchor gNB directly. Also, it should be understood that similarmethods may apply for Case 1-B, when the assistant gNB cannot find orconnected to the anchor gNB directly.

In the present implementation, the CN finds the anchor gNB, then theanchor gNB may build a connection to the assistant gNB. In anotherimplementation, the information transfer between the anchor gNB and theassistant gNB may bypass the CN. In yet another implementation, theanchor gNB may even release UE context, and the CN may deliver the UEcontext to the assistant gNB. In this way, the assistant gNB becomes theanchor gNB.

In yet another implementation, RRC_INACTIVE UE may make RRC statetransition from RRC_INACTIVE state to RRC_IDLE state, and perform cellselection to camp on the gNB. Afterwards, an RRC connectionestablishment may be proceeded, such that the UE enters RRC_CONNECTEDstate. Meanwhile, the CN may notify the original anchor gNB to removethe UE context.

Case 2 DL Data to RRC_INACTIVE UE Via Assistant gNB

Case 2-A: DL Data to RRC_INACTIVE UE Via Anchor gNB—Anchor gNBInitiation

FIG. 12 is a diagram illustrating DL data notification via the anchorgNB, according to an exemplary implementation of the presentapplication. Diagram 1200 includes a UE 1202, an anchor gNB 1204, anassistant gNB 1206, a target gNB 1210, and a CN 1230. In the presentimplementation, the UE 1202, anchor gNB 1204, assistant gNB 1206, targetgNB 1210, and CN 1230 in FIG. 12 may substantially correspond to the UE102, anchor gNB 104, assistant gNB 106, target gNB 110, and CN 130,respectively, in FIG. 1A.

Diagram 1200 also shows actions 1280, 1281, 1282, 1283, 1284, 1285,1286, 1287, 1288, 1289, 1290, 1291, 1292, 1293, and 1294, for DL datanotification via the anchor gNB as the RRC_INACTIVE UE 1202 moves to thegNB coverage area of the target gNB 1210 and the CN 1230 has DL data forthe RRC_INACTIVE UE 1202.

As shown in FIG. 12 , in action 1280, when the CN 1230 has DL data forthe RRC_INACTIVE UE 1202, the CN 1230 finds the anchor gNB 1204 via theUE 1202's UE context. In one implementation, when the anchor gNB 1204,as the last serving gNB, receives DL data from the UPF or DL signalingfrom the AMF of the CN 1230, the anchor gNB 1204 may page in the cellscorresponding to the RNA. The anchor gNB 1204 may send RAN paging (e.g.,using an Xn interface) to neighboring gNB(s) if the RNA includes cellsof neighboring gNB(s) (e.g., assistance gNB and/or target gNB). Theanchor gNB 1204 searches its table to find the assistant gNB 1206 of theRRC_INACTIVE UE 1202. In action 1281, the anchor gNB 1204 sends a DLData Notification, which carries the RRC resume ID and/or I-RNTI of theRRC_INACTIVE UE 1202, to the assistant gNB 1206.

Upon receiving the DL Data Notification, the assistant gNB 1206 beginsto send RAN-based UE Discovery messages carrying the RRC resume IDand/or I-RNTI to all gNBs in the UE 1202's RAN notification list. TheRAN notification list may be the new or updated RAN notification list asdescribed with reference to Case 1-A and/or Case 1-B. Each gNB receivingthe RAN-based UE Discovery sends a RAN-based UE Paging message, whichcarries the RRC resume ID and/or I-RNTI, to find the RRC_INACTIVE UE1202. As shown in FIG. 12 , in action 1282, the assistant gNB 1206 sendsa RAN-based UE Discovery message carrying the RRC resume ID and/orI-RNTI to the target gNB 1210 in the UE 1202's RAN notification list. Inaction 1283, the target gNB 1210 send a RAN-based UE Paging message,which carries the RRC resume ID and/or I-RNTI, to the RRC_INACTIVE UE1202. Once the RRC_INACTIVE UE 1202 receives the RAN-based UE Pagingmessage, it identifies the target gNB 1210, which it receives theRAN-based UE Paging message from, as its target gNB, and replies with aRAN-based UE Paging Response in action 1284. Only the gNB (i.e., thetarget gNB 1210) receiving the RAN-based UE Paging Response may reply tothe assistant gNB 1206 with a RAN-based UE Discovery Response messagecarrying the RRC resume ID and/or I-RNTI, as shown in action 1285.

The assistant gNB 1206, in action 1286, notifies the anchor gNB 1204with a DL Data Response carrying the RRC resume ID and/or I-RNTI andtarget gNB cell ID (RAN area ID or tracking area ID). After knowingwhich RAN the RRC_INACTIVE UE 1202 is in, the anchor gNB 1204 transfersthe UE context and DL data to the target gNB 1210. In action 1287, theanchor gNB 1204 sends a UE Context Transfer Request carrying the RRCresume ID and/or I-RNTI and target gNB 1210's cell ID (RAN area ID ortracking area ID) to the CN 1230. In action 1288, the CN 1230 sends theUE Context and DL Data Forward carrying the RRC resume ID and/or I-RNTI,UE context, DL data, and the UE 1202's RAN notification list (e.g.,having a list of gNB cell IDs (RAN area IDs or tracking area IDs)) tothe target gNB 1210. In action 1289, the CN 1230 also sends a UE ContextTransfer Response carrying the RRC resume ID and/or I-RNTI to the anchorgNB 1204. In action 1290, the anchor gNB 1204 sends a DL Data Confirmmessage carrying the RRC resume ID and/or I-RNTI to the assistant gNB1206, and deletes any information regarding to the RRC_INACTIVE UE 1202,such as UE context and the pair of UE ID and assistant gNB. Uponreceiving the DL Data Confirm message, the assistant gNB 1206 deletesthe UE ID and its RAN notification list. Once the target gNB 1210receives the UE context and DL Data Forward from the CN 1230, its storesthe UE context and the RRC_INACTIVE UE 1202's RAN notification list. Inaction 1291, the target gNB 1210 replies to the CN 1230 with a UEContext and DL Data Forward Confirm message carrying the RRC resume IDand/or I-RNTI. Thus, the connection between the target gNB 1210 and CN1230 is established, and the connection between the anchor gNB 1204 andCN 1230 (e.g., S1-MME, N2) is released. In action 1292, the target gNB1210 also updates the latest RAN notification list to the RRC_INACTIVEUE 1202 through a RAN Notification List Update. In action 1293, theRRC_INACTIVE UE 1202 confirms the received updated RAN notification listthrough a RAN Notification List Response. Thereafter, the target gNB1210 starts to receive DL data traffic from the CN 1230, and sends theDL data to the UE 1202 in action 1294. It's noted that in action 1283,action 1292 or action 1294, the UE 1202 may stay in RRC_INACTIVE state,or be indicated by the target gNB 1210 to transition to RRC_CONNECTEDstate, for DL data transmission and reception.

Case 2-B: DL Data to RRC_INACTIVE UE Directly Via Assistant gNB—CNInitiation

FIG. 13 is a diagram illustrating DL data notification directly to theassistant gNB, according to an exemplary implementation of the presentapplication. Diagram 1300 includes a UE 1302, an anchor gNB 1304, anassistant gNB 1306, a target gNB 1310, and a CN 1330. In the presentimplementation, the UE 1302, anchor gNB 1304, assistant gNB 1306, targetgNB 1310, and CN 1330 in FIG. 13 may substantially correspond to the UE102, anchor gNB 104, assistant gNB 106, target gNB 110, and CN 130,respectively, in FIG. 1A.

Diagram 1300 also shows actions 1380, 1381, 1382, 1383, 1384, 1385,1386, 1387, 1388, 1389, 1390, 1391, 1392, and 1393, for DL datanotification directly to the assistant gNB 1306 as the RRC_INACTIVE UE1302 moves to the gNB coverage area of the target gNB 1310 and the CN1330 has DL data for the RRC_INACTIVE UE 1302. Different from diagram1200 in FIG. 12 , in diagram 1300, the CN 1330 knows the assistant gNB1306 of the UE 1302, it can directly send a DL Data Notification to theassistant gNB 1306 without routing through the anchor gNB 1304, as shownin action 1381. Upon receiving RAN-based UE Discovery Response from thetarget gNB 1310 as indicated in action 1385, the assistant gNB 1306directly sends a DL Data Response to the CN 1330 in action 1386. Itshould be noted that, in the present implementation, the CN 1330 informsthe anchor gNB 1304 to release the UE context at a later stage, forexample, in action 1389. It is noted that in action 1383, action 1391 oraction 1293, the UE 1302 may stay in RRC_INACTIVE state, or be indicatedby the target gNB 1310 to transition to RRC_CONNECTED state, for DL datatransmission and reception.

It should be understood that Cases 2-A and 2-B of DL Data toRRC_INACTIVE UE via Assistant gNB may be applied not only to Case 1-A asdescried above, but also to Case 1-B.

Case 3 UL Data From RRC_INACTIVE UE—Direct Approach

FIG. 14 is a diagram illustrating UL data from the RRC_INACTIVE UE tothe target gNB, which includes assistant gNB update and UE contexttransfer, according to an exemplary implementation of the presentapplication. Diagram 1400 includes a UE 1402, an anchor gNB 1404, anassistant gNB 1406, a target gNB 1410, and a CN 1430. In the presentimplementation, the UE 1402, anchor gNB 1404, assistant gNB 1406, targetgNB 1410, and CN 1430 in FIG. 14 may substantially correspond to the UE102, anchor gNB 104, assistant gNB 106, target gNB 110, and CN 130,respectively, in FIG. 1A.

Diagram 1400 also shows actions 1480, 1481, 1482, 1483, 1484, 1485,1486, 1487, 1488, 1489, 1490, 1491, and 1492, for UL data from theRRC_INACTIVE UE to the target gNB, as the RRC_INACTIVE UE 1402 moves tothe gNB coverage area of the target gNB 1410 and has UL data for thetarget gNB 1410. In the present implementation, when the RRC_INACTIVE UEmoves into the coverage area of a target gNB, it is assumed that theRRC_INACTIVE UE does cell (re)selection and camps on the target gNB. Asshown in FIG. 14 , in action 1480, the RRC_INACTIVE UE 1402 moves intothe coverage area of the target gNB 1410, and camps on the target gNB1410. When the RRC_INACTIVE UE 1402 needs to access (e.g., send uplinkdata) a gNB (e.g., the target gNB 1410) that is not the last serving gNB(e.g., the anchor gNB 1404), in action 1481, the RRC_INACTIVE UE 1402starts a RACH procedure with the target gNB 1410, which can be a 2-stepor 4-step RACH procedure. The RRC_INACTIVE UE 1402 sends the RRC resumeID and/or I-RNTI and anchor gNB 1404's cell ID (RAN area ID or trackingarea ID) either in MSG1 of the 2-step RACH procedure shown in FIG. 3A,or in MSG1/MSG 3 of the 4-step RACH procedure shown in FIG. 3B. Thesmall data can be transmitted either in MSG1 of the 2-step RACHprocedure shown in FIG. 3A, or in MSG1/MSG 3 of the 4-step RACHprocedure shown in FIG. 3B, or in dedicated uplink resources after RRCconnection establishment or resume procedure such as PUSCH. In action1482, the target gNB 1410 triggers a procedure (e.g., an XnAP RetrieveUE context procedure) to retrieve the UE context from the anchor gNB1404. For example, the target gNB 1410 sends a UE Context Requestcarrying the RRC resume ID and/or I-RNTI to the anchor gNB 1404. Inaction 1483, the anchor gNB 1404 sends a UE Context Transfer Requestcarrying the RRC resume ID and/or I-RNTI and the target gNB's cell ID(RAN area ID or tracking area ID) to the CN 1430. In action 1484, theanchor gNB 1404 also sends a UE Context Confirm message carrying the RRCresume ID and/or I-RNTI to the target gNB 1410. Based on the UE context,in action 1485, the CN 1430 sends a UE Context Transfer message carryingthe RRC resume ID and/or I-RNTI, UE context, and a list of gNB cell IDs(RAN area IDs or tracking area IDs) to the target gNB 1410. In action1486, the target gNB 1410 stores the UE's RAN notification list andreplies a UE Context Confirm message carrying the RRC resume ID and/orI-RNTI to the CN 1430.

In action 1487, the CN 1430 sends a UE Context Transfer Confirm messagecarrying the RRC resume ID and/or I-RNTI to the anchor gNB 1404. Inaction 1488, the anchor gNB 1404 sends a UE Assistance Delete messagecarrying the RRC resume ID and/or I-RNTI to the assistant gNB 1406. Theassistant gNB 1406 then deletes the information of the UE 1402 and itsRAN notification list, and then sends a UE Assistance Delete Confirmmessage to the anchor gNB 1404 in action 1489. Upon receiving the UEAssistance Delete Confirm message, the anchor gNB 1404 also deletes theUE context and the information of the UE 1402 and its assistant gNB1406. Regarding to the target gNB 1410, which also becomes the anchorgNB and assistant gNB, in action 1490, the target gNB 1410 sends a RANNotification List Update carrying a list of gNB cell IDs (RAN area IDsor tracking area IDs) to the RRC_INACTIVE UE 1402. In action 1491, theUE 1402 replies a RAN Notification List Response to the target gNB 1410.Since the target gNB 1410 has identified the UE 1402 via the UE context,and the connection between the target gNB 1410 and the CN 1430 hasestablished, the target gNB 1410 can receive and forward UL data fromthe UE 1402 and forwards the UL date to the CN. The UL data transmissionmay begin either via RACH procedure or in dedicated UL resources. It isnoted that in action 1490 or action 1492, the UE 1402 may stay inRRC_INACTIVE, or be indicated by the target gNB 1410 in RACH procedure.In one example, the UE 1402 may transition to RRC_CONNECTED state for ULdata transmission and reception. In another example, the UE 1402 maytransition to RRC_IDLE state. In some embodiments, the action 1490 andaction 1491 may take place after uplink data transmission. For example,after the uplink data transmission and the UE 1402 transitions toRRC_INACTIVE state, the action 1490 and action 1491 are needed toconfigure the UE 1402 with the RAN notification list.

It should be understood that Case 3 for UL Data from the RRC_INACTIVE UEmay be applied to not only to Case 1-A as descried above, but also toCase 1-B.

FIG. 15 illustrates a block diagram of a node for wirelesscommunication, in accordance with various aspects of the presentapplication. As shown in FIG. 15 , node 1500 may include transceiver1520, processor 1526, memory 1528, one or more presentation components1534, and at least one antenna 1536. Node 1500 may also include a RadioFrequency (RF) spectrum band module, a base station communicationsmodule, a network communications module, and a system communicationsmanagement module, input/output (I/O) ports, I/O components, and powersupply (not explicitly shown in FIG. 15 ). Each of these components maybe in communication with each other, directly or indirectly, over one ormore buses 1540.

Transceiver 1520 having transmitter 1522 and receiver 1524 may beconfigured to transmit and/or receive time and/or frequency resourcepartitioning information. In some implementations, transceiver 1520 maybe configured to transmit in different types of subframes and slotsincluding, but not limited to, usable, non-usable and flexibly usablesubframes and slot formats. Transceiver 1520 may be configured toreceive data and control channels.

Node 1500 may include a variety of computer-readable media.Computer-readable media can be any available media that can be accessedby node 1500 and include both volatile (and/or non-volatile) media andremovable (and/or non-removable) media. By way of example, and notlimitation, computer-readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatile(and/or non-volatile) and removable (and/or non-removable) mediaimplemented in any method or technology for storage of information suchas computer-readable instructions, data structures, program modules orother data.

Computer storage media may include RAM, ROM, EEPROM, flash memory (orother memory technology), CD-ROM, digital versatile disks (DVD) (orother optical disk storage), magnetic cassettes, magnetic tape, magneticdisk storage (or other magnetic storage devices), etc. Computer storagemedia does not comprise a propagated data signal. Communication mediatypically embodies computer-readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism and includes any informationdelivery media. The term “modulated data signal” may mean a signal thathas one or more of its characteristics set or changed in such a manneras to encode information in the signal. By way of example, and notlimitation, communication media includes wired media such as a wirednetwork or direct-wired connection, and wireless media such as acoustic,RF, infrared and other wireless media. Combinations of any of the aboveshould also be included within the scope of computer-readable media.

Memory 1528 may include computer-storage media in the form of volatileand/or non-volatile memory. Memory 1528 may be removable, non-removable,or a combination thereof. Exemplary memory includes solid-state memory,hard drives, optical-disc drives, etc. As illustrated in FIG. 15 ,memory 1528 may store computer-readable, computer-executableinstructions 1532 (e.g., software codes) that are configured to, whenexecuted, cause processor 1526 to perform various functions describedherein, for example, with reference to FIGS. 1A through 14 .Alternatively, instructions 1532 may not be directly executable byprocessor 1526 but be configured to cause node 1500 (e.g., when compiledand executed) to perform various functions described herein.

Processor 1526 (e.g., having processing circuitry) may include anintelligent hardware device, e.g., a central processing unit (CPU), amicrocontroller, an ASIC, etc. Processor 1526 may include memory.Processor 1526 may process data 1530 and instructions 1532 received frommemory 1528, and information through transceiver 1520, the base bandcommunications module, and/or the network communications module.Processor 1526 may also process information to be sent to transceiver1520 for transmission through antenna 1536, to the networkcommunications module for transmission to a core network.

One or more presentation components 1534 presents data indications to aperson or other device. Exemplary one or more presentation components1534 include a display device, speaker, printing component, vibratingcomponent, etc.

From the above description, it is manifest that various techniques canbe used for implementing the concepts described in the presentapplication without departing from the scope of those concepts.Moreover, while the concepts have been described with specific referenceto certain implementations, a person of ordinary skill in the art wouldrecognize that changes can be made in form and detail without departingfrom the scope of those concepts. As such, the described implementationsare to be considered in all respects as illustrative and notrestrictive. It should also be understood that the present applicationis not limited to the particular implementations described above, butmany rearrangements, modifications, and substitutions are possiblewithout departing from the scope of the present disclosure.

What is claimed is:
 1. A method for a radio access network (RAN) basednotification area (RNA) update for a radio resource control(RRC)_INACTIVE user equipment (UE) in an RRC_INACTIVE state, the methodcomprising: receiving, by the RRC_INACTIVE UE in the RRC_INACTIVE state,a first list of RAN area identities (IDs) from a first cell; receiving,by the RRC_INACTIVE UE in the RRC_INACTIVE state, first identificationinformation broadcast by a second cell, the first identificationinformation including a RAN area ID of the second cell and a cell ID ofthe second cell; and performing, by the RRC_INACTIVE UE in theRRC_INACTIVE state, a 4-step random access procedure with the secondcell to transmit second identification information to the second cellafter determining that the RAN area ID of the second cell does notbelong to the first list of RAN area IDs, wherein a Message 3 (MSG3) ofthe 4-step random access procedure includes the second identificationinformation.
 2. The method of claim 1, further comprising: determining,by the RRC_INACTIVE UE in the RRC_INACTIVE state, that the RRC_INACTIVEUE in the RRC_INACTIVE state is moving from a first RNA to a second RNAwhen the cell ID of the second cell or the RAN area ID of the secondcell does not match any of a list of cell IDs or the first list of RANarea IDs.
 3. The method of claim 1, further comprising: initiating, bythe RRC_INACTIVE UE in the RRC_INACTIVE state, an RNA update procedureafter determining that the RAN area ID of the second cell does notbelong to the first list of RAN area IDs; and receiving, by theRRC_INACTIVE UE in the RRC_INACTIVE state, RNA information from thesecond cell during the RNA update procedure, the RNA informationincluding at least one of the following: a second list of RAN area IDs;a list of cell IDs; and a list of tracking area IDs.
 4. The method ofclaim 1, wherein the second identification information comprises aninactive-radio network temporary identifier (I-RNTI).
 5. A base stationfor a radio access network (RAN) based notification area (RNA) update,the base station comprising: at least one memory storing a set ofinstructions; and at least one processor coupled to the at least onememory, the at least one processor configured to execute the set ofinstructions to: transmit first identification information of a secondcell to a radio resource control (RRC)_INACTIVE user equipment (UE) inan RRC_INACTIVE state, the first identification information including aRAN area identity (ID) of the second cell and a cell ID of the secondcell; and receive, from the RRC_INACTIVE UE in the RRC_INACTIVE state,second identification information of a first cell during a 4-step randomaccess procedure of an RNA update procedure with the RRC_INACTIVE UE inthe RRC_INACTIVE state, wherein a Message 3 (MSG3) of the 4-step randomaccess procedure includes the second identification information.
 6. Thebase station of claim 5, wherein the at least one processor is furtherconfigured to execute the set of instructions to: transmit at least oneof an inactive radio network temporary identifier (I-RNTI) and the cellID of the second cell to the first cell.
 7. The base station of claim 5,wherein the at least one processor is further configured to execute theset of instructions to: receive, from a third cell, an RNA response;receive, from a core network (CN), a UE-specific RNA response includinga list of RAN area IDs; and transmit the list of RAN area IDs to theRRC_INACTIVE UE in the RRC_INACTIVE state after determining that a firstsecurity key included in the RNA response from the third cell matches asecond security key included in the UE-specific RNA response.
 8. Thebase station of claim 5, wherein the at least one processor is furtherconfigured to execute the set of instructions to: transmit RNAinformation to the RRC_INACTIVE UE in the RRC_INACTIVE state during theRNA update procedure, the RNA information including at least one of thefollowing: a list of RAN area IDs; a list of cell IDs; and a list oftracking area IDs.
 9. The base station of claim 5, wherein the secondidentification information comprises an inactive radio network temporaryidentifier (I-RNTI).
 10. The base station of claim 9, wherein the atleast one processor is further configured to execute the set ofinstructions to: transmit a second I-RNTI to the RRC_INACTIVE UE in theRRC_INACTIVE state during the RNA update procedure.
 11. A user equipment(UE) in a radio resource control (RRC)_INACTIVE state for performing aradio access network (RAN) based notification area (RNA) update, the UEcomprising: at least one memory storing a set of instructions; and atleast one processor coupled to the at least one memory, the at least oneprocessor configured to execute the set of instructions to: receive afirst list of RAN area identities (IDs) from a first cell; receive firstidentification information broadcast by a second cell, the firstidentification information including a RAN area ID of the second celland a cell ID of the second cell; and perform a 4-step random accessprocedure with the second cell to transmit second identificationinformation to the second cell after determining that the RAN area ID ofthe second cell does not belong to the first list of RAN area IDs,wherein a Message 3 (MSG3) of the 4-step random access procedureincludes the second identification information.
 12. The UE of claim 11,wherein the at least one processor is further configured to execute theset of instructions to: determine that the RRC_INACTIVE UE in theRRC_INACTIVE state is moving from a first RNA to a second RNA when thecell ID of the second cell or the RAN area ID of the second cell doesnot match any of a list of cell IDs or the first list of RAN area IDs.13. The UE of claim 11, wherein the at least one processor is furtherconfigured to execute the set of instructions to: initiate an RNA updateprocedure after determining that the RAN area ID of the second cell doesnot belong to the first list of RAN area IDs; and receive RNAinformation from the second cell during the RNA update procedure, theRNA information including at least one of the following: a second listof RAN area IDs; a list of cell IDs; and a list of tracking area IDs.14. The UE of claim 11, wherein the second (I-identification informationcomprises an inactive radio network temporary identifier RNTI).